Multicast Broadcast SN Synchronization Across Cells During UE Mobility

The patent introduces a core network node as an intermediary to allocate L2 SNs for NR MBS services. The core network node distributes the same L2 SN allocation information to multiple radio access network nodes, enabling synchronized L2 SN allocation across different cells without requiring strict time synchronization between the cells themselves. This mediator approach resolves the contradiction by centralizing the synchronization function.

The patent merges the L2 SN allocation function across multiple cells by having the core network node centrally allocate and distribute the same L2 SN sequence to all radio access network nodes serving the same MBS service. This ensures that regardless of which cell a UE is receiving from, the L2 SN sequence remains consistent, preventing packet loss and repetition during mobility while maintaining independent cell operation.

The patent segments the synchronization function into two independent layers: L1 physical layer transmission can occur independently in each cell without strict time synchronization, while L2 layer SN allocation is synchronized through core network control. This segmentation allows NR MBS service to achieve necessary synchronization for packet identification without requiring the strict time synchronization protocol of MBSFN, making the system adaptable to NR requirements.